micro-nanostructures. Ultrasonics Sonochemistry, (2018). 42. · maintained, showing the role of sonochemistry to modulate both morphology and dimensions of . 2 the resulting crystalline

This is the submitted version of the following article:

Hayati P., Suárez-García S., Gutierrez A., Sahin E., Molina D.R.,Morsali A., Rezvani A.R.. Sonochemical synthesis of two novelPb(II) 2D metal coordination polymer complexes: New precursorfor facile fabrication of lead(II) oxide/bromidemicro-nanostructures. Ultrasonics Sonochemistry, (2018). 42. :310 - . 10.1016/j.ultsonch.2017.11.037,

which has been published in final form athttps://dx.doi.org/10.1016/j.ultsonch.2017.11.037 ©https://dx.doi.org/10.1016/j.ultsonch.2017.11.037. Thismanuscript version is made available under the CC-BY-NC-ND4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

1

Sonochemical Synthesis of Two Novel Pb(II) 2D Metal Coordination

polymer Complexes: New Precursor for Facile Fabrication of

Lead(II) Oxide/Bromide Micro-Nanostructures

Payam Hayati a, c

, Salvio Suárez-García

c, Angel Gutierrez

d, Daniel Ruiz Molina

c*, Ali Morsali

b*,

Ali Reza Rezvania*

a Department of Chemistry, Faculty of Sciences, University of Sistan and Baluchestan, P.O.

Box 98135-674, Zahedan, Iran.

bDepartment of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-

4838, Tehran, Islamic Republic of Iran.

cCatalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, Campus

UAB, Bellaterra, 08193 Barcelona, Spain

eDepartamento de Quimica Inorganica I Facultad de Ciencias Quimicas Universidad

Complutense 28040-Madrid Spain.

Abstract

Two new lead(II) coordination polymer compounds (CSCs) (2D), [Pb2(L)2(Br)2]n·H2O (1),

[Pb2(HL/)(L

/)(H2O)2]n·H2O (2), where L= C6H5NO2 (2-pyridinecarboxylic acid) and L

/= C9H6O6

(1,3,5-tricarboxylic acid),

have been synthesized under different experimental conditions.

Micrometric crystals (bulk) or microsized materials have been obtained depending on using the

branch tube method or sonochemical irradiation. All materials have been characterized by

scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD), FT-IR

spectroscopy. Single crystal X-ray analyses on compounds 1 and 2 show that Pb2+

ions are 8-

coordinated, 7 and 9-coordinated, respectively. Topological analysis shows that the compound 1

to 2 are 4,6L26, and bnn net, respectively. However, neither the shape nor the morphology is

maintained, showing the role of sonochemistry to modulate both morphology and dimensions of

2

the resulting crystalline material, independently of whether we have a 2D coordination polymer.

Finally, micro/structuration of lead(II) bromide oxide and lead(II) oxide have been prepared by

calcination of two different lead (II) CPs at 700 °C that were characterized by scanning electron

microscopy (SEM) and X-ray powder diffraction (XRD).

Keywords: Coordination polymer compounds, Sonochemical process, Ultrasound irradiation,

Nano particle, Topology, Morphology.

1. Introduction

Coordination polymer compounds (CSCs) are presently of considerable interest and importance

because of the scope they offer for the generation by design of new materials with a range of

potentially useful properties [1,4]. Some very interesting types of CSCs with cyclic structures

based on the concept of molecular squares using metal ions and bridging ligands containing N-

donors including 4,4′-bipyridine, 4,4′-trimethyllenedipyridine, 1,2-bis(4-pyridyl)ethane,

pyrazine, and related species have been reported [5-8]. Another strategy to obtain analogue

coordination polymers with cavity or porosity structures is the reaction of metal ions with

multifunctional ligands containing O-donors such as polycarboxylates. As a building block to

create some porous or cyclic coordination polymer, trimesate (tma) ligand exhibits various

coordination fashions and the capability of forming coordination architectures of diverse sizes

and shapes. Although there were a lot of reports [9-12], on the infinite 1D, 2D, and 3D CSCs

assembled by N and O donor ligands, up to now their functionalities remain, with the exception

of several reports, largely unexplored. The CSCs of different metal ions could be synthesized

through various methods, such as the diffusion-based method, layering technique, evaporation

route, hydrothermal synthesis, crystallization technique and ultrasonic irradiation method [13-

21]. Sonochemistry originates from the extreme transient conditions induced by ultrasound,

3

which produces unique hot spots that can perform temperatures above 5000 K, pressures

exceeding 1000 atm, and heating and cooling rates in excess of 1010 K s-1

. These conditions are

distinct from other conventional synthetic techniques for instance photochemistry, wet

chemistry, hydrothermal synthesis or flame pyrolysis. The speed of sound in a typical liquid is

1000 to 1500 ms-1

, and ultrasonic wavelengths will vary from roughly 10 cm down to 100 mm

on the frequency range of 20 kHz to 15 MHz, much larger than the molecular size scale. The

chemical and physical effects of ultrasound therefore arise not from a direct interaction between

chemical species and sound waves, but rather from the physical phenomenon of acoustic

cavitation: the formation, growth, and implosive collapse of bubbles [22-26].

The synthesis of lead(II) systems is an increasingly active area due to presence of the 6s2 electron

configuration and stereo activity with the valence shell lone electron pair and based on directed

ligands classify as holodirected and hemidirected [27-33]. Lead possesses unique coordination

versatilities with ligands and the synthesis of the related complexes at the nanoscale can open

novel applications in the field of roofing, batteries and solder. So far, examples of [Pb(NNO)2]n ,

[Pb(NNO)(SCN)]n (HNNO = nicotinic acid N-oxide) [34] , [Pb(µ-L)(µ-X)2]n (X = Cl,Br,I)

(L=N,N′-bis(4-pyridylmethylidyne) phenylene-1,4-diamine [35], [Pb(μ-bdabpm)(μ-Br)2]n

([bdabpm = 1,4-Benzenediamine, N,N′-bis(3-pyridinylmethylene)]) [36],

{[Pb3(BOABA)2(H2O)]·H2O}n, {[Pb4(BOABA)2(µ4-O)(H2O)2]·H2O}n,(H3BOABA=3,5-bis-

oxyacetate-benzoic acid) [37], [Pb(μ-4,4′-bipy)(μ-Br)2]n , [Pb(μ-bpa)(μ-Br)2]n, [Pb(μ-bpe)(μ-

Br)2]n , (4,4′-bipy= 4,4′-bipyridine, bpa= 1,2-bis(4-pyridyl)ethane) [38], [Pb(μ-bpp)(μ-Br)2]n

(bpp = 1,3-di(4-pyridyl)propane) [39], [Pb2(µ-I)2(µ-dpp-N,N,N,N)(µ-dpp-N,N)I2]n (dpp=2,3-

bis(2-pyridyl)pyrazine) [40], [Pb2(TPAA)(HTPAA)(NO3)]·6H2O,

[Pb2(TPAA)(HTPAA)2]·DMF·0.5H2O (DMF = N, N-Dimethylformamide, H2TPAA=4-(1, 2, 4-

4

triazol-4-yl) phenylarsonic acid) (2) [41], rare lead (II) coordination supramolecular compounds

with different ligand are reported. However, the synthesis of lead-based 2D coordination

polymers still represents a challenge. In this manuscript, we have developed a simple

sonochemical approach to prepare the novel lead(II) coordination polymers [Pb(L)(SCN)]n (1)

and [Pb2(L/)2(SCN)4]n (2) the resulting crystalline material is compared with that alternatively

obtained by the branch tube methodology. Morphology was investigated and results compared

with each other. Also, these compounds were used for preparation of Pb3O2Br2 and PbO

microparticles by using calcination process.

2. Experimental

2.1. Materials and physical techniques

Starting reagents for the synthesis were purchased and used without any purification from

industrial suppliers (Sigma–Aldrich, Merck and others). Elemental analyses (carbon, hydrogen,

and nitrogen) were performed employing a Heraeus Analytical Jena, Multi EA 3100 CHNO

rapid analyzer. Fourier transform infrared spectra were recorded on a Bruker Tensor 27 FT-IR

with a single window reflection of diamond ATR (Attenuated total reflectance) model MKII

Golden Gate, Specac and the OPUS data collection programme software. The instrument is

equipped with a room temperature detector, and a mid-IR source (4000 to 400 cm-1

). Since it is a

single beam instrument, it was needed to run a background spectrum in air before the

measurement. Single crystal X-ray diffraction experiments were carried out for compounds 1 and

2 with MoKα radiation (=0.71073 Å) at ambient temperature. A micro focused Rigaku mm003

source with integrated confocal caxFlux double bounce optic and HPAD Pilatus 200K detector

were used for Pb3O2Br2 and PbO ( (1-1, 1-2 , 1-3) and (2-1, 2-2, 2-3), respectively) while for two

data were measured on a Bruker-Nonius Kappa CCD diffractometer. The structures were solved

5

by direct methods and refined by full matrix least squares on F2. All non-hydrogen atoms were

refined anisotropically. The hydrogen atoms were included with fixed isotropic contributions at

their calculated positions determined by molecular geometry, except for the oxygen bonded

hydrogen atoms, which were located on a difference Fourier map and refined riding on the

corresponding atoms. (Computing details: data collection, cell refinement and data reduction:

CrystalClear-SM expert 2.1b43 [42]; program(s) used to solve structure: SHELXT; program(s)

used to refine structure: SHELXL-2014/7 [43]; molecular graphics: PLATON [44]; reduction of

data and semiempirical absorption correction: SADABS program[45]; direct methods (SIR97

program[46]); full-matrix least-squares method on F2: SHELXL-97 program [47] with the aid of

the programs WinGX [48] and Olex2[49]). X-ray powder diffraction (XRD) measurements were

performed using an X’pert diffractometer manufactured by Philips with monochromatized Cukα

radiation and simulated XRD powder patterns based on single crystal data were prepared using

the Mercury software. The samples were characterized with a scanning electron microscope

(SEM) (FEI Quanta 650 FEG) in mode operation of secondary electrons (SE) with a beam

voltage between 15 and 20 kV. The samples were prepared by deposition of a drop of the

material previously dispersed properly solvents on aluminium stubs followed by evaporation of

the solvent under ambient conditions. Before performing the analysis, the samples were

metalized by depositing on the surface a thin platinum layer (5 nm) using a sputter coater (Leica

EM ACE600). A multi wave ultrasonic generator (Elmasonic (Elma) S40 H), equipped with a

converter/transducer and titanium oscillator (horn), 12.5 mm in diameter, operating at 20 kHz

with a maximum power output of 400 W, was used for the ultrasonic irradiation.

6

2.2. Synthesis of [Pb2(L)2(Br)2]n.H2O (1) as single crystals by branch tube method

Pb(NO3)2 (1 mmol, 0.331g), 2-pyridinecarboxylic acid (L) (1 mmol, 0.123g) and KBr (2 mmol,

0.238g) were loaded into one arm of a branch tube and both of the arms were filled slowly by

water. The chemical bearing arm was immersed in an oil bath kept at 60 °C. Crystals were

formed on the inside surface of the arm kept at ambient temperature after. After 5 days, colorless

crystals were deposited in the cooler arm were filtered off, washed with water and air dried.

(0.198g, 47.93% yield based on final product), product 1 (single crystal): Anal. Calc. for

C12H8Br2N2O4Pb2·0.5(H2O): C: 17.46, H: 1.08, N:3.38 %; Found C: 17.35, H: 1.04, N:3.28 %.

IR (selected bands for compound 1; in cm-1

):3562(w), 3069(w), 1750(s), 1656(w), 1154(s).

2.3. Synthesis of [Pb2(L)2(Br)2]n.H2O (1) under ultrasonic irradiation

To prepare the microstructures of [Pb2(L)2(Br)2]n (2) by sonochemical process, a high-density

ultrasonic probe was immersed directly into the solution of Pb(NO3)2 (10 ml, 0.1 M) in water,

then into this solution, a proper volume of KBr (10 ml, 0.1 M) and 2-pyridinecarboxylic acid (L)

(10 ml, 0.1M) ligand in water solvent was added in a drop wise manner. The solution was

irradiated by sonicate with the power of 60W, concentration of reactant 0.1M and temperature 30

°C for 30 min. For the study of the effect of time the initial reagents on size and morphology of

nanostructured complex 1, the above processes were done with 60 min and for the study of the

effect of temperature with 60°C (time: 30 min, sonication power: 60W, concentration: 0.1M).

The obtained precipitates were filtered, subsequently washed with water and then dried.

Complex 1-1: (0.290 g, 70.20% yield based on final product), product 1-1: Anal. Calc. for


7

IR (selected bands for compound 1-1; in cm-1

): 3548(w), 3053(w), 1721(w), 1648(s), 1187(w),

705.51(s).




): 3574(w), 3014(w), 1762w), 1632(s), 1169(w).




): 3556(w), 3082(w), 1730(w), 1618(s), 1137(w).

2.4. Synthesis of [Pb2(HL/)(L

/)H2O]n.H2O (2) as single crystal by branch tube method

Pb(NO3)2 (0.5 mmol, 0.165 g), 1,3,5-benzentricarboxylic acid (H3L) (0.5 mmol, 0.105 g) were

loaded into one arm of a branch tube and both of the arms were filled slowly by water. The arm

containing the reagents was immersed in an oil bath kept at 60 °C. After 12 days colorless

crystals of 2 were formed on the inside surface of the arm kept at ambient temperature. They

were filtered off, washed with water and air dried. (0.154 g, 34.92% yield based on final

product), product 2 (single crystal): Anal. Calc. for (C18 H11 O14 Pb2)n·H2O: C: 24.44, H: 1.24,

O: 25.34%; Found C: 24.36, H: 1.12 O: 24.68 %. IR (selected bands for compound 1; in cm-1

):

3560(br), 3105(br), 1696(s), 1533(s), 1362(w).

2.5. Synthesis of [Pb2(HL/)(L

/)H2O]n.H2O (2) under ultrasonic irradiation

A high-density ultrasonic probe was immersed directly into a water solution of 1,3,5-

benzentricarboxylic acid (H3L) (30 ml, 0.01 M), then into this solution, a proper volume of

Pb(NO3)2 in water (30 ml, 0.01 M) was added in a drop wise manner. The solution was

8

irradiated by sonicate with the power of 60W, concentration of reactant 0.01M and temperature

30 °C for 30 min.

For the study of the effect of time the initial reagents on size and morphology of microstructured

complex 2, the above processes were done with 60 min and for the study of the effect of

temperature with 60°C (time: 30 min, sonication power: 60W, concentration: 0.01M). The

obtained precipitates were filtered, washed with water and dried in air.

Complex 2-1: (0.198 g, 44.89% yield based on final product), product 2-1: Anal. Calc. Anal.

Calc. for (C18H11O14Pb2)n·H2O: C: 24.44, H: 1.24, O: 25.34%; Found C: 24.19, H: 1.09 O: 25.18

%. IR (selected bands for compound 1; in cm-1

): 3550(br), 3101(br), 1680(s), 1522(s), 1358(w).

Complex 2-2: (0.236 g, 53.49% yield based on final product), product 2-2 Anal. Calc. for

(C18H11O14Pb2)n·H2O: C: 24.44, H: 1.24, O: 25.34%; Found C: 24.37, H: 1.17 O: 25.22 %. IR

(selected bands for compound 2-2; in cm-1

): 3542(w), 3110(w), 1687(s), 1548(s), 1364(w).


(C18H11O14Pb2)n·H2O: C: 24.44, H: 1.24, O: 25.34%; Found C: 24.37, H: 1.17 O: 25.22 %. IR

(selected bands for compound 2-3; in cm-1

): 3538(w), 3108(w), 1679(s), 1562(s), 1356(w).

2.6. Synthesis of Pb3O2Br2 as nanoparticles by thermal decomposition of complex 1

The preparation of Pb3O2Br2 calcinations of complex 1 was done at 700 °C in static atmosphere

of air for 4 h. Powder XRD diffraction shows that calcination was completed and the entire

complexes were decomposed.

9

2.7. Synthesis of PbO nanostructures by thermal decomposition of complex 2

Microparticles of complex 2 transferred to a crucible. The crucible was transferred to furnace

and heated at 700 ºC under static atmosphere of air for 4 h. The furnace was cooled to 25ºC. The

organic components were combusted and PbO microstructures were produced. The XRD pattern

shows the product is PbO.

3. Results and discussion

A 2D CSCs [Pb2(L)2(Br)2]n.H2O (1) was obtained by reaction of L= C6H5NO2 (2-

pyridinecarboxylic acid), potassium bromide with lead(II) nitrate in water. The coordination

polymer (CP) [Pb2(HL/)(L

/)H2O]· H2O (2), was obtained by the reaction between the organic

oxygen-donor ligand and lead(II) nitrate, which yielded in crystalline material formulated as new

coordination polymer. Utilizing 1,3,5-tricarboxylic acid (L/) ligand in lead (II) nitrate leads to

formation of new molecular CP [Pb2(HL/)(L

/)H2O]n.H2O (2). Microstructures of new complexes

were obtained in aqueous solution by ultrasonic irradiation. Single crystals of new compounds,

suitable for X-ray crystallography, were prepared by thermal gradient method applied to an

aqueous and methanol solution of the reagents (the ‘‘branched tube method’’). Single crystal X-

ray diffraction analysis (Tables 1- 3) of compounds 1 and 2 were carried out and the coordination

environment of the title complexes are shown in (Fig .1) Single X-ray crystal analysis reveals

that [Pb2(L)2(Br)2]n·H2O (1), and [Pb2(HL/)(L

/)H2O]n·H2O (2) complexes crystallize in

monoclinic and triclinic space group (P21/n and P-1, respectively).

The Pb atoms of complex 1 coordinate two Br atoms, one O atom and one N atom composing

distorted octahedral coordination NO3Br4 (Fig. 1). The asymmetric unit of compound 1 contains

two Pb2+

cations, which coordinate two 2-pyridinecarboxylic acid ligand (L= C6H5NO2), one

10

water molecule in water molecule lattice structure and two Br- anions (Fig. 2). The crystal

packing is composed of one crystallographically different [Pb(L)(Br)] units, labelled A, showing

the same coordinative features and alternating along the a-crystal direction. Ligands are bridging

neighboring lead atoms and the consecutive A units, giving rise to a 2D network. One L ligand,

unit A, is coordinated in a chelating way with the nitrogen in the vertex of the pyramid and one

oxygen atom in the basal plane. All the picolinate ligands show the same bridging-chelating

coordination scheme leading to the formation of a one dimensional chain: …–Pb1–O3–Pb2–O1–

Pb1–… along the crystal a axis. There is an additional Pb-Br interaction along the chain, with

short contacts of 3.451 Å (Pb1–Br2) and 3.395(3) Å (Pb2–Br1) that are blocking the exposed

coordinative position of the lead atoms (Fig 3, 4 and table 2). The coordination environment of

the lead atoms is completed by two bromine atoms that are bridging Pb1 and Pb2 ions of

different chains, thus extending the polymer along the baxis (Fig 5). Furthermore, there are

hydrogen bound between O(4) and H(9) in each layer [H(9)-O(4) distance of 2.037 Å].

Additionally, H-bonds connect the layers in 1 into 3D (along (0,1,0) direction) framework.

Obviously, hydrogen and π – π interactions play major role in formation of the layer packaging

(Fig. 6).

Simultaneously every 2-pyridinecarboxylic acid ligand and Br- anion is bridging and

coordinated by two Pb2+

cations. Coordination bonds form tetramer ring-shaped complex

[Pb2(L)2(Br)2]n·H2O (Fig.1 and 8). According to ToposPro package the underlying topology of

the complex is 2,4L2, which is abundant for 2D CP (more than 75 examples in TTO collection

of ToposPro (Fig. 9) [50-51]. Every [Pb2(L)2(Br)2]n.H2O layer is surrounded by two other same

complexes forming van-der-waals bonded and hydrogen bound (Fig. 9).

11

In complex 2, Pb atoms are coordinated by seven and nine O atoms have pentagonal

bipyramidal and triaugmented triangular prism structure and coordination sphere as O7 and O9,

respectively (Fig.1). The asymmetric unit of compound 2 contains two Pb2+

cations, which

coordinate two 1,3,5-tricarboxylic acid ligand and one H2O molecule (Fig. 2). Each 1,3,5-

tricarboxylic acid ligand in compound 2 is coordinated to two Pb atom by O atom of carbonyl

and hydroxide group, and Pb–O distance is about 2.51-2.90Å (Table 3 and Fig. 3). Also, shows

compound 2 is two-dimensional coordination polymer complex. For four Pb+2

cations, there are

π-π interactions with each other. Four molecules contacts by two aromatic rings (L), in fact L is

linker and connected by carboxylate groups. Obviously π-π interactions play major role in

formation of the molecular by surrounding each molecule in hexagonal geometry of connection

(Fig. 5). Hydrogen bound is formed between the hydrogen of molecular water and oxygen of the

carboxylic group present in the ligand and is expanded along (1,0,0) direction. Therefore, there

are π – π interaction between aromatic rings which lead to crystal structure be stable (Fig. 7).

The coordination interactions can be separated in two groups:

i) Strong, more valence, in short range of 0.930-2.717Å;

ii) Weak, more electrostatic, in long range of 3.085-3.801Å.

Structures of compound 2 is two-periodic ((1,1,0) orientation) coordination polymer

architectures, respectively. To understand the global topological motif for connection of ligands

and metal atoms into periodic networks we performed topological analysis by program package

ToposPro. For this goal the underlying net in standard representation was constructed [50]. Thus,

the underlying net for compound 2 is represented by 3-coordinated nodes from HL and L

ligands, as well as 7 and 9-coordinated Pb2+

ions. The 2D net belongs to topological type of bnn

12

hexagonal, Shubnikov plane net (Fig.8) [50-51]. Additionally, one H2O molecule is coordinated

to each Pb (II) cation with contacts distances Pb–O in the range of 2.61-2.94 Å (Table 3 and Fig.

3). 1,3,5-tricarboxylic acid ligand is located between two layer (2D) and is connected through O

atoms carbonyl and hydroxide of carboxylic acid (functional group) (Fig. 9). Figure 10 shows a

fragment of the 3D framework in complexes 1 and 2.

The IR spectra display characteristic absorption bands for 2-pyridinecarboxylic acid ligand

and H2O in compounds and 1. The relatively weak absorption bands to compound 1 about 3000

cm−1

result from the O-H stretching frequency carboxylic acid group ligand. The absorption

bands with variable intensity in the frequency range 1700-1750 cm−1

correspond to C=O

stretching frequency of the carbonyl from the 2-pyridinecarboxylic acid ligand. Also, the

characteristic band of the C-O stretching frequency carboxylic acid group appears at 1000-1300

cm−1

. The IR spectrum of compound 1 shows the characteristic stretching frequency of H2O

group observed at around 3574 cm−1

. For compound 2 two bands around 1500-1700 cm−1

are

due to the C=C stretching frequency amine group ligand. (Fig. 11).

For compound 2 the IR spectra display characteristic absorption bands for H2O and the 1,3,5-

benzentricarboxlic acid ligand in compound 2. The relatively weak absorption bands to

compound 2 about 3500 cm-1

result from the stretching frequency H2O group. Additionally, the

relatively weak absorption bands to compound 2 about 3000 cm-1

result from the O–H stretching

frequency carboxylic acid group ligand. The absorption bands with variable intensity in the

frequency range 1700–1750 cm-1

correspond to C=O stretching frequency of the carbonyl from

the 1,3,5-benzentricarboxlic acid ligand. The absorption bands around 1448 and 825 cm-1

are

related to stretching of C=C and =C-H bending of aromatic rings. Also, the characteristic band of

the C-O stretching frequency carboxylic acid group appears at 1000-1300 cm-1

. In summary for

13

all compounds, the elemental analysis and IR spectra of the nano-structure produced by the

sonochemical method as well as the bulk material produced by the branched tube method are

indistinguishable (Fig. 12).

Ligand-free Pb3O2Br2 and PbO microstructures were simply synthesized by solid-state

transformation of compound 1 and 2 at 700°C under air atmosphere for 4 h. Figure 13 and 14

provide the XRD pattern of the residue obtained from the calcination of compound 1 and 2. The

obtained pattern matches with the standard patterns of Pb3O2Br2 and PbO with the lattice

parameters [a =12.252(3) Å, b =5.873(1), c =9.815(3) Å, S.G. = Pnma (61) and z = 4] and [a

=5.8931(1) Å, b =5.4904(4), c =4.7528(1) Å, S.G. = Pbcm (57) and z = 4] which are the same as

the reported values (Powder diffraction file 01-087-1185 and 01-077-1971 38-1477),

respectively. As the calcination process was successful for the preparation of Pb3O2Br2 and PbO,

we used the nano-sized compounds 1 and 2 prepared by the sonochemical process at different

conditions which is written in Table 4. For the two compounds, acceptable matches, with slight

differences in 2θ, were observed between the simulated and experimental powder X-ray

diffraction patterns. This indicates that the compound 1 and 2 obtained by the sonochemical

which are initial material for preparing Pb3O2Br2 and PbO structures. The SEM images of the

microstructures obtained after the calcination are shown in Fig 15 and 16.

4. Conclusion

Two new Pb(II) CSCs, [Pb2(L)2(Br)2]n·H2O (1) and [Pb2(HL/)(L

/)(H2O)2]n·H2O (2) have

been synthesized by using a thermal gradient approach. Coordination polymers complexes 1 and

2 possess topology type and point symbol 4,6L26 and bnn net, {3^2.4^2.5^2}{3^4.4^4.5^4.6^3}

and {4^6.6^4}, respectively. Larger crystals suitable for single crystal x-ray diffraction have

been obtained by the branched tube method. Calcination method has been used to obtain

14

crystalline structures a few micron length width. Interestingly, the simulated x-ray diffraction

powder obtained from the x-ray data confirms the structure of the microcrystal obtained by

calcination method. These results confirm the potentially of ultrasound for the obtaining of

microstructures of Pb3O2Br2 and PbO.

Supplementary material

Crystallographic data for the structure reported in this paper have been deposited with the

Cambridge Crystallographic Data Centre as supplementary publication no. CCDC-1511738 and

1495799, respectively. Copies of the data can be obtained upon application to CCDC, 12 Union

Road, Cambridge CB2 1EZ, UK (Fax: +44 1223/336033; e-mail: [email protected]).

Acknowledgement

This work was supported by grant MAT 2015-70615-R from the Spanish Government and by

Feder funds. Funded by the CERCA Program / Generalitat de Catalunya. ICN2 is supported by

the Severo Ochoa program from Spanish MINECO (Grant No. SEV-2013-0295).

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21

Table 1. Crystal data and structures refinement for [Pb2(L)2(Br)2]n.H2O (1),

[Pb2(HL/)(L

/)(H2O)2]n·H2O (2).

C18H13O15Pb2 (2) C12H8Br2N2O4Pb2·0.5(H2O) (1) Empirical formula

883.68 g/mol 827.41 g/mol Formula weigh

293(2)K 296(2)K Temperature

0.71073 Å 0.71073 Å Wavelength

Triclinic Monoclinic Crystal system

1P P21/n Space group

a =9.3156 (17)Å,α=67.764 (9)°

b = 10.268 (2)Å,β=85.707 (10)°

c = 12.893 (3)Å,γ =71.778 (9)°

a = 8.6303 (7) Å,α=90.000(5)°

b = 8.5930 (7)Å, β =99.576 (5)°

c = 23.0762(19) Å,γ =90.000 (5)°

Unit cell dimensions

1083.0(4) Å3 1687.5 (2)Å3 Volume

2 4 Z

2.734 g/cm3 3.257 g/cm3 Density(calculated)

0.343 Mg/m3 24.683 Mg/m3 Absorption coefficient

810 1460 F(0 0 0)

2.9 to 28.6°

2.5 to 25.6° Theta range for data collection

15.61 mm-1

-12 ≤h ≤12

-13 ≤k ≤ 13

-17 ≤ l ≤ 17

24.68 mm-1

-11 ≤ h ≤ 9

-11 ≤ k ≤ 11

-27 ≤ l ≤ 29

Index ranges

0.674 Å−1 0.650 Å−1 (sin θ/λ)max

28.6° 25.6° Theta(max)

Mo Kα

Full–matrix least–squares on F2

1.042

Mo Kα

Full–matrix least–squares on F2

1.021

Radiation type

Refinement method

Goodness- of- fit on F2

R[F2> 2σ(F2)]=0.041

wR(F2)=0.078

S=1.04

R[F2> 2σ(F2)]=0.036

wR(F2)=0.083

S=1.02

Refinement

24099, 6412, 5072 15082, 3834, 2848 R1 [I>2(I)]

0.073

2.35, -198 eA-3

1495799

0.064

1.58 and -1.58 eA-3

1511738

Rint

Largest diff. peak and hole

CCDC no.

22

Table 2. Selected bond lengths/ Aº for compound [Pb2(L)2(Br)2]n·H2O (1)

1.393(14) C(8)—C(9) 3.131(1) Br(1)—Pb(1)

0.9300 C(9)—H(9) 3.1482(10) Br(1)—Pb(2)

1.360(13) C(9)—C(10) 3.0815(10) Br(2)—Pb(1) 0.9300 C(10)—H(10) 3.1874(10) Br(2)—Pb(2)

1.368(11) C(10)—C(11) 0.9300 C(1)—H(1)

1.517(11) C(11)—C(12) 1.378(12) C(1)—C(2)

2.587(6) O(3)—Pb(1)ii 1.338(10) C(1)—N(1)

2.458(6) O(3)—Pb(2) 0.9300 C(2)—H(2)

2.587(6) Pb(1)—O(3)iii

1.379(14) C(2)—C(3)

2.551(6) Pb(2)—O(1)iv

0.9300 C(3)—H(3)

2.701(6) Pb(2)—O(2)iv

1.425(13) C(3)—C(4)

Symmetry transformations used to generate equivalent atoms:

(i) 1.5-x, -0.5+y, 0.5-z; (ii) 0.5-x, 0.5+y, 0.5-z; (iii) 0.5-x, -0.5+y, 0.5-z; (iv) 1.5-x, 0.5+y, 0.5-z.

Table 3.Selected bond lengths/ Aº for compound [Pb2(HL/)(L/)(H2O)2]n·H2O (2)

1.252(9) O(3)—C(7) 2.516(6) Pb(1)—O(4)

1.503(10) C(9)—C(1) 2.530(8) Pb(1)—O(16)

1.513(9) C(17)—C(12) 2.567(5) Pb(1)—O(1) 1.394(11) C(12)—C(11) 2.664(5) Pb(1)—O(2)

1.398(11) C(12)—C(13) 2.717(6) Pb(1)—O(3)

1.510(11) C(16)—C(10) 2.505(5) Pb(2)—O(10)

1.393(11) C(1)—C(6) 2.532(5) Pb(2)—O(7)

1.395(11) C(1)—C(2) 2.544(6) Pb(2)—O(1)

1.504(11) C(7)—C(5) 2.610(7) Pb(2)—O(13) 1.484(10) C(18)—C(14) 2.633(6) Pb(2)—O(9)

Table 4. The influence of temperature, reaction time, concentration of initial reactant and

sonication power on the size of compounds 1 and 2 particles. The ultrasounds power used in all

reactions was 60 W.

Synthesis for complex 1 M(mol/l)a T(°C)

b t (min)

c

1 - 1 0. 1 30 30

1 - 2 0. 1 30 60

1 - 3 0. 1 60 30

Synthesis for complex 2 M(mol/l)a T (°C)

b t (min)

c

2 - 1 0.01 30 30

2 - 2 0.01 30 60

2 - 3 0.01 60 30

a Concentration of initial reactant,

b Reaction temperature,

c Reaction time,

d Average diameter (nm)

23

Figure 1. The coordination environment of Pb+2

cation environment in complexes (1) (up)

and (2) (down), respectively.

24

Figure 2. Asymmetric units complexes (1) (up) and (2) (down), respectively.

25

Figure 3. Views of complex (2), representation of coordination ligand binding along a

direction (up), representation of coordination bridging ligand in 2D network along b direction

(down).

26

Figure 4. Distance of bound in complexes (1) (up) and (2) (down).

.

27

Figure 5. 2D layers of complexes (1) and (2) (left). Interaction between layers in complexes

(1) and (2) (right).

28

Figure 6. Hydrogen bound and π – π interaction in complex (1).

29

Figure 7. Hydrogen bound and π – π interaction in complex (2).

30

Figure.8. Topological representation of coordination networks in complexes (1) (up) and (2)

(down).

31

Figure 9. The number of layer, molecules and chain surrounding the complexes (1) (up) and

(2) (down).

32

Figure 10. A fragment of the 3D framework in complexes (1) (up) and (2) (down).

33

Figure 11. FT-IR spectra of (a) micro-structured 1-1, 1-2 and 1-3

Figure 12. FT-IR spectra of (a) micro-structured 2-1, 2-2 and 2-3

34

Figure 13. (a) XRD pattern simulation of Pb3O2Br2; XRD patterns of Pb3O2Br2 which is prepared

by calcination of 1-1 (b) 1-2 (c) 1-3(d) at 700°C.

Fig. 14. (a) XRD pattern simulation of PbO; XRD patterns of PbO which is prepared by

calcination of 1-1 (a) 1-2 (b) and 1-3 (c) at 700°C.

35

Figure 15. SEM image of PbO which is prepared by calcination of (a) 1-1, (b) 1-2 and (c) 1-3at

700°C.

Figure 16. SEM image of PbO which is prepared by calcination of 2-1 (c) 2-2 (d) 2-3 at 700°C.

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micro-nanostructures. Ultrasonics Sonochemistry, (2018). 42. · maintained, showing the role of sonochemistry to modulate both morphology and dimensions of . 2 the resulting crystalline